Tension adjusting device



Aug. 4, 1942. H `J MCCARTHY TENSION ADJUSTING lDEVICE Filed Deo. 6, 1940Henry JMS Cgrtlzy INVENTOR.

i ATTORNEY Patented Aug. 4, 1942 UNITED .STATES PATENT OFFICE TENSIONADJ USTIN G DEVICE Henry J. McCarthy, Danvers, Mass., assignor toHygrade Sylvania Corporation, Salem, Mass., a. corporation ofMassachusetts Application December 6, 1940, Serial No. 368,87 6

1 Claim.

This invention relates to apparatus for adjusting thermal relays.

An object of this invention is to provide a means for obtaining a highdegree of accuracy in the timing of the relay.

Another object is to provide a means for adjusting the thermal relay soas to obtain maximum eiiciency.

A further object is to provide a means for making ne and delicateadjustments quickly and at the same time in a manner as to permit theattainment of high production.

Further objects, advantages and features will be apparent from thespecification below taken in conjunction with the accompanying drawingin which:

Figure 1 is a perspective view of the testing apparatus with a thermalrelay in position to be tested;

Figure 2 is a tus.

Similar reference characters refer to similar parts throughout theseveral views of the draw- 111g.

Since some type of thermal relay is usually used in the startingapparatus for electric gaseous discharge lamps and more particularly inuorescent lamps, in order to permit the desired preheating period forthe llamentary electrodes of the lamp, it is highly desirable that thisperiod be gauged accurately. The filaments should be heated suficientlyto be capable of carrying the discharge across the lamp, yet it is notnecessary that they be heated for any longer period.

If a thermal relay or starter switch, similar to the one described inco-pending application Serial No. 356,566, led September l2, 1940, isused, this apparatus may be used to properly gauge the tension of theresistance contact point plan 4view of the testing apparaagainst thebimetallicstrip therein employed.

Once a switch has been found in which the tension is such as to providejust the desired filament preheating period, this tension is measured onmy apparatus so that all other switches may be similarly adjusted.

Figure 1 shows the manner in which the switch is adjusted. The switch Iis inserted into position in the adjustment box 2 through the slot 3provided therefor. When the switch reaches the position shown in thisgure, it establishes electrical contact through line 5. When thepositioning arm I2 has been brought into the position here shown, thecircuit through the switch and the adjustment box becomes closed and asmall indicator light I6 will glow. 'I'his light is reend and havecessed in the slot 4 in the adjustment box 2 and indicates that thecircuit through the switch I is closed.

In actual operation in the starting apparatus for fluorescent lamps, thelength of time it will take for the bimetallic strip 6 to becomesufciently heated to break away from the carbon contact 'I will `dependon the tension which the strip 6 is exercising against the contact 1LFor example,rif the strip 6 is exercising a great tension against thecontact 1, the circuit through the switch will remain closed for alonger period and thus produce a longer preheating period than wouldresult if there were only a slight tension betwen the strip 6 and thecontact 1. The tension measuring device of my invention provides ameasure for insuring substantially the same tension in all starterswitches of the same size and type.

When it has been ascertained that a certain starter switch provides thedesired period for preheating the filaments before breaking the circuit,this switch is placed in position in the adjusting box 2, as shown inFigure 1, and the scale 8 with the spring steel finger 9 mounted thereonis swung into position, pivoting about the stud I IJ projecting from theelongated slot Il. The stud I0 may be moved forward or backward in thisslot II in order to properly locate the scale 8 and the :finger 9 inrelation to the bimetallic strip 6 depending on the size and type ofswitch being adjusted. In this device, finger 9 is pivoted about pivotI0. 'I'he positioning arm I2, pivoting on the stud I3 is swung over tohold the switch firmly in position, thus closing the circuit while thetension calculation is being made.

The rearward end of the spring finger 9 is attached to the rearward endof the scale 8 on which it is mounted. The scale 8 is calibrated inunits of force. Thus, when the forward tip I 1 of the finger 9 isbrought forward by manually pivoting it about stud I 0 and starts toexert a pressure on the bimetallic strip 6, the spring finger 9 willdeflect. The finger 9 will continue to deect until the pressure at thetip I1 of the nger 9 against the bimetallic strip 6 is great enough topush the strip away from the carbon contact and thus open the circuit.'I'he breaking of the circuit will be indicatedby the extinguishing ofthe indicator light I6.

'Ihis spring finger 9 consists of two pieces of spring steel which maybe .003 inch in thickness. They are clamped firmly together at the pivota steel tip I 1 welded at the forward extremity thereof. The use of twopieces of spring steel clamped together impart a substantially uniformdeflection as the tip l'l' exerts pressure on the bimetallic strip 6.

When the pressure on the strip 6 is suiicient to open the circuitthrough the switch I, the location of the finger 8 in relation to thecalibrated scale 8 is noted by the operator. Thus, each switchthereafter adjusted will have substantially the same tension of thestrip 6 against the contact 1. Since this tension is a determiningfactor in the calculation of the iilament preheating period, and sincethe master switch used was one proven to be highly efficient andcalculated to a high degree of accuracy, all switches may very easily betimed substantially the same by using the apparatus of my invention. Theadjustment on the various switches may be made by bending the arm I8 onthe end of which the contact 1 is carried.

Figure 2 shows the manner in which the electrical circuit may beconnected in the adjusting box 2. Spring contact pins IS and 20, locatedat the inner end of the slot 3, serve as the means for establishingelectrical contact with the base pins projecting from the bottom of theswitch l. The positioning arm l2 will be thrown over to hold the switchl firmly in position to secure positive contact. At the same time thearm l2 is thrown over, the circuit will be completed through the armcontact point 2| and the contact nger 22, whereupon the indicator lightI6 will go on. When this is accomplished the switch is ready for tensionadjustment. Y

Although I have described the manner in which my tensioning deviceoperates with reference to my copending thermal relay application, thedevice of my invention may be used as a tension adjusting means for anysimilar devices without departing from the spirit of my invention.

What I claim is:

Apparatus for measuring the tension necessary to disengage a pair ofnormally closed electrical relay elements, said apparatus comprising: abase having an elongated slot and adapted to receive an electrical relayin testing position; a stud projecting upwardly through said elongatedslot in said base, said stud being adjustably positioned in said basealong the horizontal axis thereof; a scale pivotally mounted atop saidstud; and an arm comprising a pair of elongated resilient members joinedto each other and having its rearward end fixed to the pivoted end ofsaid scale, and its forward and free end cooperating with said scale andadapted to be engaged with one of said electrical relay elements fordisengaging said elements.

HENRY J. MCCARTHY.

